Thermal-acoustic insulation materials have widely been recognized as an important member to construct comfortable and energy-saving housing or to protect humans and/or equipment from harsh external environment. Although natural fibers and synthetic resins have conventionally been used for thermal-acoustic insulation materials, these materials have a problem in safety because they are generally flammable and generate toxic fumes in case of fire.
For that reason, inorganic materials have recently been used as an alternative to natural fibers and synthetic resins. In particular, having favorable properties such as nonflammability, formability, and mountability, glass fibers have been widely used as a raw material for thermal-acoustic insulation materials.
However, since glass fibers have a specific gravity of approximately from 2.4 to 2.6 g/cm2, which is quite large, the thermal-acoustic insulation material made of glass fibers does not exhibit sufficient quality in acoustic and thermal insulation per unit mass. In addition, since glass fibers gradually deteriorate by absorbing moisture and they do not have sufficient mechanical strength, the thermal-acoustic insulation material made of glass fibers does not retain enough durability.
Meanwhile, demand for thermal-acoustic insulation materials having ample safety and high quality has immensely been increasing. For example, in high-speed transport means such as high-speed train cars, aircraft, spacecraft, and the like, high-speed and comfortableness required for such means of transport inevitably entail the demand for thermal-acoustic insulation materials having such properties as being highly safe, tough and lightweight. Specifically, the requirements besides excellent acoustic and thermal insulation quality are 1) to be lightweight, 2) to have excellent fire-resistance, 3) not to generate toxic fumes in case of fire, 4) to have no corrosiveness to structural materials, 5) to have excellent mechanical strength and compression resilience, 6) to have excellent abrasion resistance, 7) to have little hygroscopicity, and 8) to have good mountability, and so forth.
As previously mentioned, conventional thermal-acoustic insulation materials including the materials made of glass fibers are not reliable enough for the aforementioned uses. Therefore, there has been awaited the development of a highly reliable thermal-acoustic insulation material usable for the above purposes.